1. The Field of the Invention
The present invention relates to a method and apparatus for dynamically adjusting the operating parameters of a storage device used for storing computer data. More specifically, the present invention relates to dynamically adjusting the operating parameters of a storage device according to the sensed temperature of the storage device environment.
2. The Relevant Art
Computer systems generally utilize auxiliary memory storage devices having media onto which data can be written and from which data can be read for later use. A direct access storage device (DASD) incorporating rotating magnetic disks is commonly used for storing data in magnetic form on disk surfaces. Data is recorded on concentric, radially spaced tracks on the disk surfaces. Magnetic heads including write elements and read sensors are used to record the data on the disk and then read the data from the tracks on the disk surfaces. The write element and read sensor together are known as the magnetic read/write transducer.
Typically, the read/write transducer is located on a single aerodynamically shaped block of material (usually ceramic). This assembly, also referred to as the slider, flies above the surface of the disk at an extremely small distance (on the order of nanometers) as the disk rotates. The distance the lowest point of the transducer head flies above the disk surface is known to those familiar the art as the mechanical spacing of the DASD.
The write element of the transducer usually consists of an inductive transducing element having an electrical conductor winding around a magnetically permeable material. Data is written by driving a current through the conductor coil to create a magnetic field, causing a magnetic pattern representing the data to be placed on the disk surface. The current that is driven through the conductor coil is known as the write current. This current creates a changing magnetic field exiting the write head structure between the two poles formed by the write gap. The distance between this point (the write gap) and the magnetic center of the disk is known to those familiar with the art as the magnetic spacing of the DASD.
The disks used in current DASDs vary in the required field strength for writing data to them. The dominant factor that limits how easily data can be written to a disk is the coercivity of the disk. The coercivity of the disk refers to the required field strength created by the write head required to permanently change the magnetization direction of the disk. The lower the coercivity of the disk, the easier it is to write data onto the disk surface. Since the write field created by the write head is proportional to the write current under Bertram's theory of magnetic recording, less write current is required to drive the write head at lower coercivity levels.
The mechanical and magnetic spacing properties of a DASD do incur a variety of manufacturing variances (e.g. overcoating thickness, fly high variation, etc.), but once the DASD has been manufactured, for a given set of components, the variations are significantly smaller than over the population of all DASD assemblies. The coercivity of the disk, however, is a dynamic property of the disk drive. The coercivity of the disk is highly sensitive to changes in temperature as well as the flux changes attempted to be written. Current art DASDs do not take the full temperature range of the environment in which the DASD may operate into consideration when setting the write current to be used. This results in either too much or too little write current being applied to record data as the temperature of the environment in which the DASD is operating varies.
When too little write current is used, the written waveform might be substantially distorted or incomplete, leading to errors. When too much write current is applied, large fringe fields may occur at the sides of the write element. The fringe fields may cause a problem known as side writing, or curved transitions, leading to various degradations in the read-back performance. In order for DASDs to optimize storage space, the spacing between the tracks on the disk, or track density, needs to be as small as possible. The presence of fringe fields from too much write current limits the track density of a disk.
Accordingly, a need exists in the art for a dynamic write head current adjustment method and apparatus that is able to set the write current to an optimal value based upon the properties of the DASD and the environment in which the DASD operates.